Type CW Power Relay for Class 1E Applications 30

41-241.31BCW POWER RELAY

nected in such a way that current, (IA), leads voltage,(VBA), by 150 degrees when the motor is operating atunity power factor. Loss of excitation to the motorcauses a large var flow into the motor without appre-ciable change in the watt flow. As the current goesmore lagging, operation of the CW permits tripping oralarm action.

2.0 CONSTRUCTION

The relay consists of a product operated unit, aphase shifter and an indicating contactor switch(ICS), shown in Figure 1, page 6.

2.1 PRODUCT TYPE UNIT

The electromagnet for the main element has atapped current coil located on the center leg of an “E”type laminated structure and two potential coils onthe outer legs. This is shown schematically in Figure2, page 6. Operating torque is obtained by energizingthe tapped coil with line current and the two outercoils with line potential from the line potential trans-formers. Out of phase air gap fluxes necessary tooperating torques are produced by a phase shiftingnetwork in conjunction with the potential coils. Maxi-mum torque occurs when the current leads the volt-age by 30 degrees as illustrated in Figure 3, page 7.The voltage is independent of the direction of powerflow. This provides a reference so that the disc canrotate in either direction depending upon direction ofthe line current. The combination of voltage and cur-rent produces an operating torque proportional topower.

2.1.1 Phase Shifter - The phase shifter networkconsist of a resistor in series with the potential coils.

2.2 INDICATING CONTACTORSWITCH UNIT (ICS)

The dc indicating contactor switch is a small clappertype device. A magnetic armature, to which leaf-springmounted contacts are attached, is attracted to themagnetic core upon energization of the switch. Whenthe switch closes, the moving contacts bridge two sta-tionary contacts, completing the trip circuit. Also dur-ing this operation two fingers on the armature deflect aspring located on the front of the switch, which allowsthe operation indicator target to drop. The target isreset from the outside of the case by a push-rodlocated at the bottom of the cover.

The front spring, in addition to holding the target, pro-vides restraint for the armature and thus controls thepickup value of the switch.

3.0 CHARACTERISTICS

The type CW relays are available in the followingranges and taps:

Typical 60 hertz Time-Power Curves are shown in fig-ures 4 & 5 page 8. The curves are taken at maximumtorque which occurs with the current leading the volt-age by 30 degrees (within ± 4°).

3.1 TRIP CIRCUIT

The main contacts will safely close 30 amperes at250 volts dc and the seal-in contacts of the indicatingcontactor switch will safely carry this current longenough to trip a circuit breaker.

The indicating instantaneous trip contacts will safelyclose 30 amperes at 250 volts dc, and will carry thiscurrent long enough to trip a breaker.

3.2 TRIP CIRCUIT CONSTANTS

Indicating Contactor Switch Coil.

4.0 SETTINGS

The watt tap and the time dial setting must beselected.

The connector screw on the terminal plate above thetime dial makes connections to various turns on theoperating coil. By placing this screw in the various

VoltsLine-

to-Line

(IL VLL)

Range Taps

12020 - 120

100 - 600 20 - 30 - 40 - 60 - 80 - 100 - 120100 - 150 - 200 - 300 - 400 - 500 - 600

20835 - 200

175 - 1000 35 - 50 - 70 - 100 - 140 - 175 - 200175 - 250 - 350 - 500 - 700 - 875 - 1000

Ampere Pickup

Ohms dc Resistance

0.2 8.5

1.0 0.37

2.0 0.10

3 single phase watts( )

2


terminal plate holes, the relay will respond to multi-ples of tap value watts in accordance with the varioustypical time-watts curves, ± 5%.

CAUTION!Since the tap block connector screw carriesoperating current, be sure that the screw isturned tight.

In order to avoid opening current transformer circuitswhen changing taps under load, the relay must befirst removed from the case. Chassis operating short-ing switches on the case will short the secondary ofthe current transformer. The taps should then bechanged with the relay outside of the case and thenre-inserted into the case.

4.1 OVERWATT APPLICATION

The CW for three phase application has taps whichrepresent the minimum balanced three phase wattsdivided by that will cause the disc to move. Tapvalue is also voltamperes at which the disc will beginto move with current leading voltage applied to therelay by 30 degrees. When connected for watt sens-ing the relay current leads relay voltage by 30degrees when the system current and line-to-neutralvoltage are in phase.

Assume:

RC = ct ratio = 600:5 = 120RV = vt ratio = 4200:120 = 35P = power = 1000 primary kilowatts (3Ø) desired

trip level

Direct Solution:

Indirect Solution:

Use tap 150 (closest to 137.5) on 100-600 watt relay.

Time dial 2 will give 2 second operation at 2182 kilo-watts. See Figure 4, page 8.

4.2 MOTOR LOSS OF FIELD APPLICATION

The usual setting of the CW relay for this application(Figure 7, page 10) is 20 watts, time dial 2 on the20-120 watt relay. When, on loss of field, the motorpower factor goes approximately 30 degrees lagging(watts and vars into the motor) and more, the con-tacts of the CW close after the time delay establishedby the time dial setting.

In this application, the CW would operate duringmotor starting and a field breaker 41a switch may beused to prevent this by controlling the voltage circuit.This allows the motor to be accelerated, and the fieldbreaker closed before the CW close after the timedelay established by the time dial setting.

Note that the use of field breaker 41a switch control,prevents loss of field detection on accidental fieldbreaker opening. Other provisions must be incorpo-rated to trip the controller when 41a is used and thefield breaker opens following field application. If 41ais not used directly, it may drive a timer that closesthe coil circuit when 41 closes and has time delayrelease when 41 opens.

This same relay will detect loss of synchronism in thefirst slip cycle provided the slip frequency is suffi-ciently low that the CW current stays in the “operate”area long enough to produce operation.

4.3 INDICATING CONTACTOR SWITCH (ICS)

There are no settings to make on the indicating con-tactors with (ICS).

Close the main relay contacts and pass sufficient dccurrent, through the trip circuit to close the contactsof the ICS. This value of current should not begreater than the particular ICS nameplate rating. Theindicator target should drop freely.

Repeat above except pass 85% of ICS nameplaterating current. Contacts should not pickup and targetshould not drop.

5.0 INSTALLATION

The relays should be mounted on switchboard pan-

3

T P

RCRV 3--------------------- 1 000 000, ,

120 35( ) 3--------------------------- 137.5= = =

IPP

3VLL

----------------- 1 000 000, ,3 4160

--------------------------- 138.8 a primary= = =

IS 138.8 120⁄ 1.157 a secondary= =

VS 4160 35⁄ 118.86 volts line-to-line= =

T ISVS 1.157 118.86( ) 137.5= = =

P 150 137.5 1000( )⁄ 1091 kW actural= =

3


els or their equivalent in a location free from dirt,moisture, excessive vibration and heat. Mount therelay vertically by means of the four mounting holeson the flange for the semi-flush type FT case. Themounting screws may be utilized for grounding therelay. External toothed washers are provided for usein the locations shown on the outline and drilling planto facilitate making a good electrical connectionbetween the relay case, its mounting screws and therelay panel. Ground wires should be affixed to themounting screws as required for poorly grounded orinsulating panels. Other electrical connections maybe made directly to the terminals by means of screwsfor steel panel mounting.

For detail information on the FT case refer to I.L.41-076 for semi-flush mounting.

6.0 ADJUSTMENT AND MAINTENANCE

For an Acceptance Test use the following informationas appropriate.

The proper adjustments to insure correct operation ofthis relay have been made at the factory and shouldnot be disturbed after receipt by the customer. If theadjustments have been changed, the relay takenapart for repairs, or if it is desired to check the adjust-ments at regular maintenance periods, the instruc-tions below should be followed carefully.

All contacts should be cleaned periodically. A contactburnisher Style Number 182A836H01 is recom-mended for this purpose. The use of abrasive mate-rial for cleaning contacts is not recommended,because of the danger of embedding small particlesin the face of the soft silver and thus impairing thecontact.

6.1 PRODUCT UNIT

NOTE: A spring shield covers the reset spring of theproduct unit. To remove the spring shield, requiresthat the damping magnet be removed first. Thescrew connection holding the lead to the moving con-tact should be removed next. The second screwholding the moving contact assembly should then beloosened not removed.

CAUTION!This screw terminates into a nut held captivebeneath the molded block. If screw is removed,difficulty will be experienced in the re-assemblyof the moving contact assembly.) Slide thespring shield outward and remove from relay.Tighten the screw holding the moving contactassembly to the molded block.

6.2 CONTACT

The index mark on the movement frame will coincidewith the “0” mark on the time dial when the stationarycontact has moved through approximately one-half ofits normal deflection. Therefore, with the stationarycontact resting against the backstop, the index markis offset to the right of the “0” mark by approximately.020”. The placement of the various time dial posi-tions in line with the index mark will give operatingtimes as shown on the respective time-watt curves.

6.2.1 Minimum Trip Volt Amperes - Set the timedial to position 6. Using the lowest tap setting, alter-nately apply tap value volt amperes plus 3% and tapvalue volt amperes minus 3% with the current leadingthe voltage by 30°. The moving contact should leavethe backstop at tap value plus 3% and should returnto the backstop at tap value minus 3%. The relayshould be calibrated with 10 times tap value at thenumber six time dial position. Check several pointson the typical time curves. Time curve calibration isaffected by adjusting the position of the permanentmagnet keeper. Note that with current leading volt-age by 30 degrees the actual watts applied to therelay are .866 times tap value at pickup.

6.3 INDICATING CONTACTOR SWITCH (ICS)

Initially adjust unit on the pedestal so that armaturefingers do not touch the yoke in the reset position(viewed from top of switch between cover and frame).This can be done by loosening the mounting screw inthe molded pedestal and moving the ICS in thedownward position.

a) Contact Wipe – Adjust the stationary contact sothat both stationary contacts make with the mov-ing contacts simultaneously and wipe 1/64” to3/64” when the armature is against the core.

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b) Target – Manually raise the moving contacts andcheck to see that the target drops at the sametime as the contacts make or up to 1/16” ahead.The cover may be removed and the tap holdingthe target reformed slightly if necessary. How-ever, care should be exercised so that the targetwill not drop with a slight jar.

C) Pickup – The unit should pickup at 98% ratingand not pickup at 85% of rating. If necessary, thecover leaf springs may be adjusted. To lower thepickup current use a tweezer or similar tool andsqueeze each leaf spring approximately equal byapplying the tweezer between the leaf spring andthe front surface of the cover, at the bottom ofthe lower window.

If the pickup is low, the front cover must beremoved and the leaf spring bent outwardequally.

7.0 RENEWAL PARTSRepair work can be done most satisfactorily atthe factory. However, interchangeable parts canbe furnished to the customers who are equippedfor doing repair work. When ordering partsalways give the complete nameplate data.

5

Current Coil Ratings:

RangeAmperes

Continuous 1 Sec

20-120 Watt Range35-200 Watt Range

5 A 230 A

100-600 Watt Range175-1000 Watt Range

8 A 370 A

Relay Range Potential Circuit Current Circuit

Watts Voltage VoltamperesCurrentlags by

CurrentRelayTap

VoltamperesCurrentlags by

20 - 120100 - 600

120120

17.917.9

60°60°

5 amp.5 amp.

20100

16.25.4

78°77°

35 - 200175 - 1000

208208

18.818.8

59°59°

5 amp.5 amp.

35175

16.25.4

78°77°


PHOTO

ICS

PHASE SHIFT RESISTOR

WATT TAPS

DAMPING MAGNET

Figure 1: Front View of Type CW Power Relay without Case (photo)

Sub 43518A63

Figure 2: Internal Schematic of the Type CW Relay in Type FT-11 case

6


Sub 1849A304

Figure 3: Current and Voltage Phasors at System Unity Power Factor Applied to Type CW relay

7


8

Sub

135

36A

53S

ub 1

3536

A52

Fig

ure

4:T

ypic

al 6

0 H

ertz

Tim

e C

urve

s of

the

21-1

20 a

nd th

e 35

-200

wat

t typ

e C

W R

elay

.
F
igur

e 5:

Typ

ical

60

Her

tz T

ime

Cur

ves

of th

e 10

0-60

0 an

d 17

5-10

00 w

att t

ype

CW

Rel

ay.


* Sub 6184A811

Figure 6: External Schematic of Three Type CW Relays on a Three-Phase System

Note: For Balanced Three-Phase Conditions only One CW Relay is required.

9


Sub 3774B831

Figure 7: External Schematic of a Three-Phase Connection of One CW Relay for Loss of Field Protection

10


Sub 3849A303

NOTE:MAXIMUM TORQUE ANGLE IN THE TRIPPING DIRECTION OCCURS WHEN THE

CURRENT LEADS THE VOLTAGE BY 30 DEGREES WITH CONNECTIONS AS SHOWN.

TYPE CW RELAY(FRONT VIEW)

125 VOLT TEST SOURCE ROTATION A, B, C

1

2

3

4

5

6

7

8 10+

+

PHASESHIFTER

ICS

SWITCH

9

A

+

+V I

PHASEANGLEMETER

A.C.T.

RHEOSTAT

V

VARIABLEAUTO -

TRANSFORMER

ICS

CW

CWCW

Figure 8: Diagram of Test Connections for Type CW Relay in FT-11 Case

11

Documents

Type CW Power Relay for Class 1E Applications 30